The use of radio frequency identification (RFID) to identify one of a plurality of items is well known. Typically RFID Tags consist of a semiconductor device, formed in one or more materials such as an organic semiconductor, for example a doped polyanyline, an inorganic semiconductor such as doped amorphous silicon or a doped crystal silicon, and an antenna, capable of receiving energy in the near field, far field or both.
The semiconductor circuit performs functions such as the rectification of energy from a reader device to provide some or all of the power for the device, receive circuits to accept commands from a reader system if required, a logic circuit to store an identification code and a method of sending information back to a reader, such as varying the semiconductors impedance presented to the antenna, typically described as backscatter modulation. The above described device is commonly described as an RFID chip. The RFID Chip maybe directly attached to the antenna or attached via an electric field coupling, a magnetic field coupling or a combination of both. Alternatively, the RFID Chip may be first attached to a structure having two or more electrical leads, which is then attached to an antenna by either direct connection, an electric field coupling, a magnetic field coupling or a combination of both. This is typically referred to as a “strap” or “interposer”. The RFID Chip stores data, which can include identifying data unique to a specific item, which is accessed by a device commonly described as a reader or interrogator.
RFID tags can be attached to items for inventory control, shipment control, and the like. RFID tags are particularly useful in identifying, tracking and controlling items such as packages, pallets, and other product containers. The location of each item can be tracked and information identifying the owner of the item or specific handling requirements, can be encoded into the RFID tag and accessed by a reader in a suitable location, such as a portal for taking goods in and out of a building, or by a hand-held device.
RFID tags have been incorporated into a pressure sensitive adhesive-backed label for items contained in temporary packaging, such as cardboard cartons, or containers which are to undergo a number of reuses, such as pallets, waste containers, shipment containers and the like. These labels are fabricated by attaching an antenna made of metal foil or other suitable material to a substrate material such as paper, film and the like, also referred to as an inlay substrate.
Construction of an RFID device can include an RFID chip or strap that is attached to the substrate in cooperative disposition with the antenna to form what is typically referred to as an RFID tag inlay. Exemplary RFID inlays are available from Avery Dennison RFID Company of Clinton, S.C. and sold under the trade designation “AD” followed by a model or part number. An adhesive is then applied to the surface of the inlay substrate over the antenna and RFID chip, and the inlay substrate may then be attached directly to a substrate or article or may be made or incorporated into a label substrate, on which text and graphics can be imprinted, so that the adhesive, antenna and RFID chip are sandwiched between the inlay substrate and the label substrate. A layer of adhesive is then applied to the surface of the label substrate over the inlay, followed by the addition of a release layer over the adhesive to form a laminate.
The laminate can then be die cut to the finished label size. Printing of a bar code or other information, text and graphics onto the finished label, and coding of the RFID Tag can take place before or after the die cutting step. The labels are then wound tightly onto a spool or processed into a fan-fold configuration for shipment to a customer or return to the electronic manufacturer or marketer. The application of the inlay to the paper is usually carried out by an electronic manufacturer and the remaining steps are typically carried out by a label manufacturer.
Traditionally, RFID tags are produced as self-contained devices, including both a strap and antenna, where the antenna is a significant cost in the assembly. Additionally, effective coupling of the antenna and the strap must be achieved for the RFID tag to be operable. That is, specific antennas are designed for particular end use applications. This requires a great deal of precision due to the relative size of the components and may also lead to a large inventory in order to accommodate the demands of a broad customer base. Furthermore many RFID tags are permanently affixed to particular items and cannot be recovered for reuse.